For a generation of children immersed in technology, emerging research suggests that while the temptation to multitask may be pervasive, the ability to control it could be the real bellwether of academic success.

Those under 18 multitask more often and more extensively than previous generations, says Larry D. Rosen, the author of the 2012 book iDisorder: Understanding Our Obsession With Technology and Overcoming Its Hold on Us. On average, he found, 13- to 18-year-olds use more than six types of media simultaneously during out-of-school time.

The pervasiveness of technology and social media, coupled with a fear of missing out on something important, has led students to pay "continuous partial attention" to everything, but has resulted in their having difficulty concentrating deeply on anything, according to Mr. Rosen and other researchers who took part in the Web-Connected Minds Conference, held near Washington this month.

They highlighted emerging research on the way the brain copes with doing too much.

Brain Reaction Time

Simply put, the brain can't be in two places at once.

High Multitaskers Perform Poorly

Just because students think they are great multitaskers doesn't mean they can juggle many tasks at once, as a study published in the Proceedings of the National Academy shows. Researchers tested "low" and "high" multitaskers among college students identified based on the number of different media they reported regularly using simultaneously.

SOURCE: Proceedings of the National Academy

Not only can people not process two tasks simultaneously, but it also takes longer to multitask than it would to do the individual tasks one after the other, according to Steven G. Yantis, the chairman of the psychological and brain sciences department at Johns Hopkins University in Baltimore.

It's fine to walk and chew gum at the same time, but when a person tries to do two things at the same time that each require a choice, there's a brief "bottleneck" in the prefrontal cortex—the decisionmaking part of the brain—that delays the second task, he said.

In most situations, that delay is only milliseconds long. Yet the newer the task, the more dynamic the environment, and the more intense the distraction, the longer it will take the brain to react.

In the case of an adolescent driver, Mr. Yantis said he found that texting could slow reaction time by a full second, which at high speed is "halfway into the trunk of the car in front of you."

In education, that delay can cause students to miss information or simply fail to fully take it in. Research shows teachers shouldn't necessarily take students' word for it that having multiple media helps, rather than hurts, their concentration.

In a landmark 2009 study in the Proceedings of the National Academy of Sciences, Stanford University researchers compared the attention-switching abilities of people who said they multitasked often with those of people who did so rarely. It found that the frequent multitaskers were more easily distracted and performed worse on memory and attention tests than those who preferred to do one thing at a time.

"There appears to be an intrinsic, structural aspect of brain function that prevents perfect task-sharing," Mr. Yantis said at the May 4-6 conference, which was held in Arlington County, Va., and sponsored by the Needham, Mass.-based Learning and the Brain Society.

"If you are reading a chapter and have to answer a text message, your attention is on the chapter," Mr. Yantis explained. When a text message or email alert goes off, the student has to switch attention to the phone or computer, read and understand the message, respond and then return to the textbook.

"Part of this switch time is remembering what you were reading, getting your head back into the task of reading, not just moving your eyes," Mr. Yantis said.

That delay is even more pronounced in students with attention deficit hyperactivity disorder, according to research from Mr. Yantis' colleague Dr. Martha B. Denckla, the director of developmental cognitive neurology at the Kennedy Krieger Institute in Baltimore and a pediatric neurology professor at Johns Hopkins.

"It's ironic, but hyperactive children are slow," Dr. Denckla said. "Multiple-task interference is greater in children with ADHD; it costs them more. As they have to respond, evaluate, and move along, they have a harder time doing it."

Younger people generally are better at multitasking than older people because working memory tends to peak in the early 20s, said Daniel T. Willingham, a psychology professor at the University of Virginia, in Charlottesville. But he doesn't buy the idea that students who have grown up surrounded by technology have an edge or need to do more than one thing at once.

"There's not much reason to think they are better at multitasking than previous generations," Mr. Willingham said in a separate interview before the conference.

"If you practice doing A and B like crazy, you might get better at doing those two things at once, exactly because you get to know exactly the moments when it's better to switch from A to B," he said.

For example, a National Institute for Child Health and Human Development study of multitasking drivers found that experienced adult drivers stopped trying to dial a number as they approached a traffic light, and they tended to have fewer accidents or near-misses than teenage drivers, who would finish the call before looking back at the road.

"Working memory depends strongly on how well you can control selective attention and ignore distraction," Mr. Yantis said. "High-value distraction significantly slows performance."

New 'Marshmallow Test'

In a famous study, Stanford University researchers tested preschoolers' self-control by asking them to hold off eating one marshmallow for 15 minutes in exchange for two sweets at the end of the wait. Fewer than one-third of the 4-year-olds tested had the self-control to wait, but those who did showed academic and social success in the years that followed.

Texting seems to have become the new "marshmallow test" for older students, and with similar results.

In a 2011 study, researchers led by Mr. Rosen, who is a psychology professor at California State University, Dominguez Hills, randomly assigned 185 young college students with A and B grade averages to watch a video lecture, on which they knew they would be tested. During critical sections of the lecture, the researchers texted each student either four or eight times with questions that had nothing to do with the lecture and asked them to respond "promptly," or did not text them at all.

Students who received eight text messages scored more than 10 percent lower on the test, about the equivalent of a full letter grade.

Yet students' response times to the text messages made a big difference in how well they did. Students who answered the texted questions within five minutes of receiving them—while the critical material was presumably being discussed—answered 75 percent or fewer correct on the test, while those who held off five minutes or more scored 85 percent correct.

Researchers led by Fang-Yi Flora Wei, an assistant broadcast communications professor at the University of Pittsburgh's Bradford, Pa., campus, likewise found students with greater self-control were less likely to text in class and more likely to attend to content. Ms. Wei's study is published in the April issue of the journal of the National Communication Association, Communication Education.

Skills and Tactics

Mr. Rosen argues that parents and educators cannot simply remove technology and other distractions; they are too intricately woven into students' daily lives, particularly in middle and high school. Rather, he said, students should learn metacognitive skills to help them understand when and how to switch their attention between multiple tasks or technologies.

Whether or not today's students grow up intrinsically better adapted to multitasking, they will need to develop that skill to cope in the modern economy, according to Cathy N. Davidson, the author of the 2011 book Now You See It: How the Brain Science of Attention Will Transform the Way We Live, Work, and Learn.

Working collaboratively with other students requires intense multitasking, she said, involving negotiating, debating, and explaining while juggling data and class assignments, often via multiple media, such as online videoconferencing and texting.

"We are well trained to a certain kind of attention: task-specific attention, silent and alone," Ms. Davidson said. "Where in the workplace do we ever do things silently and alone? We live in a connected world."